Whenever a patient lays in bed for a prolonged period of time, especially for decreased mobility patients who stay mostly in the same position, the skin tissue of the patient can begin to breakdown. Some of the most common factors that contribute to skin tissue breakdown are continuous pressure on any part of the body, friction or shear on the skin, prolonged moisture against the skin and elevated temperatures. For example, when a portion of the body is subjected to a continuous pressure, the blood supply to skin tissue can be cut off. As a result, the tissue is deprived of oxygen and nutrients, which, in turn, can cause the tissue to begin to die and can cause pressure sores to develop.
There are treatments commonly used to avoid tissue breakdown by avoiding or minimizing the factors that lead to skin tissue breakdown. For instance, alternating pressure therapy is used in support surfaces to address continuous pressure. Alternating pressure therapy involves changing the loading characteristics/pressure points of the support surface. In other words, alternating pressure therapy redistributes pressure in a support surface so that pressure is not constantly concentrated on certain portions of the body (i.e., the boney prominences) of a patient. As a result, the flow of blood and oxygen is not cut off.
Support surfaces adapted to provide alternating pressure therapy are known. In such support surfaces, a plurality of foam-filled air cells is operatively connected to a pump. The pump inflates every other air cell on a given cycle time. Once the inflation time of a first group of air cells is completed, the pump switches to inflating a second group of air cells. The second group of air cells is pressurized while the first group of cells evacuates air back through the pump. The constant changes in relative elevation between the pressurized air cells and the adjacent non-pressurized air cells creates changing points of elevated pressure in localized areas and results in pressure relief and/or pressure redistribution.
To reduce the effects of temperature and moisture, low air loss therapy is used. Low air loss therapy affects the micro-climate around the skin, either by direct air flow to the skin or by cooling and reducing the moisture in the support surface itself. As a result, the skin of the patient is less susceptible to maceration and, accordingly, is less prone to damage from tearing from friction or shear.
Low air loss therapy is typically achieved by using spacer fabrics or air permeable materials in a top cover of the support surface. The top cover is connected to a pump. Generally, the pump supplies air into the top cover. The air travels upward through the spacer material. The air flow removes moisture/humidity from below and around the patient. However, one problem with current designs of providing low air loss therapy in a top cover is the uneven distribution of air around the patient. The top cover is depressed under the body and limits the amount of air flow. Also, the air may only enter the top cover at one point, such as at the foot of the bed. As a result, in some cases, little if any air reaches the upper torso of the patient due to air flow constrictions and/or drag. The actual area effectively served by low air loss in such designs is small compared to the area of the bed surface. Higher loaded and/or more deformed areas of the mattress relative to certain zones of the anatomy may actually pinch off the air flow/circulation in those areas which may actually be some of the most critical/at risk areas of the body.
Through utilization of various therapy modes, specific risk factors can be addressed, which can provide beneficial outcomes. It is generally known that providing a plurality of therapies continuously and at the same time to simultaneously address multiple risk factors can favorably affect outcomes better than if a plurality of therapies is only applied sequentially (not simultaneously) but repetitively.
There are all air support surfaces (that is, those that are not filled with any supporting material) on the market today in which both the therapies of alternating pressure and low air loss is combined into a single system with one pump and can be used simultaneously. However, this is not the case for foam mattresses that utilize air cylinders which are filled with foam. Such air/foam systems either require two pumps, one for each therapy. Alternatively, such systems have a single pump but only one therapy can be used at a time. Again, while many systems are available that can provide alternating pressure as well as low air loss therapies in a single support surface, they require the use of one or the other therapy at a time or necessitate multiple pumps.
Thus, there is, therefore a need for a single pump system that integrates low air loss therapy into a conventional foam/air cylinder which also is capable of operating alternating pressure at the same time.